Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSVOLVO2004S80 L6-2.9L TURBO VIN 91 B6294TREPAIR AND DIAGNOSISA L L DIAGNOSTIC TROUBLE CODES ( DTC )TESTING AND INSPECTIONMANUFACTURER CODE CHARTSECM CODES (ENGINE CONTROL MODULE)ECM-4901DIAGNOSTIC TROUBLE CODE (DTC) INFORMATION
2004 Volvo S80 L6-2.9L Turbo VIN 91 B6294T
Diagnostic Trouble Code (DTC) Information
2004 Volvo S80 L6-2.9L Turbo VIN 91 B6294TSECTION Diagnostic Trouble Code (DTC) Information
Diagnostic trouble code (DTC) information
Condition
The control module continuously checks three-way catalytic converter (TWC) effectiveness by comparing signals from the rear heated oxygen sensor (HO2S) with the front heated oxygen sensor (HO2S). Diagnostic trouble code (DTC) ECM-4901 is stored if three-way catalytic converter (TWC) efficiency deviates too much.
Substitute value
Rear heated oxygen sensor (HO2S) is disabled.
Possible source
- misfiring
- air leakage in the intake system
- air leakage in the exhaust system
- faulty fuel pressure?
- uneven compression?
- defective three-way catalytic converter (TWC)
Fault symptom[s]
- malfunction indicator lamp (MIL) lit
RENDER: 1.0x
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.